I played your map and I liked it. There were a few things however I think could possibly be tweaked.
1. The core of Lyoko. It was attacked 0 times the first time I played and 1 time the 2nd time i played (I belive i gave each game around 40ish mins each before destroying the replicas). While it was a pain in the neck to get to it and fend off the mantas I found a quick loophole that lets me easily ignore the core all together. Returning to the past also heals the core, I dont know if this was intentonal or not, but it makes the cores "defense" really easy. Pehaps up the frequency of attacks and mabye* make it so it doesnt heal, or just heals less?
2. I played singleplayer and set myself to pink/Aelita and got control of Y/U/O's units and had them sit in town and defend. Aelita can solo the whole entire lyoko part herself EASILY. She might die a time or 2 while destroying the replicas but thats bassically it. She can just put her barrier on and avoid a confrontation and easily make it into the towers, she can also plow right through the replicas as i mentioned before. Mabye alter her a little or somthing?
3: While A/Y/O can target area and devirtulize themselves from lyoko, Ulrich has no such means. While you could always get one of the others to devirtulize him you might wana either let him be able to target himself, or add in a way for the gang to get back from lyoko without dying/returning to the past.
Now for another suggestion/question:
Do you have any intentions of making any of these characters part of the map? Franz Hopper/Schiphizoa (SP?)/Good william/collossus/Sissi (Sissi Mainly cuz i want to have Yumi punch her face in XD) a part of the map?
Now for the things I really liked and want to compliment you/others on who worked on the map... and more suggestions to help out XD:
1:The custom modles are very very nice (Except poor odd, hes just an old blood mage but the blood mage does still bear a resembalance to odd), and generally rezemble there actualy lyoko selves (especially Yumi).
2: Always love the theme song WWD. Perhaps you could play the ending song that plays at the end of the latter episodes at the end of the map? If you dont have it, it can be found at:
Code Lyoko - Free Music Downloads - MP3 Downloads - Download.com Music
Overall I really like it and cant think of any more suggestions for you at the moment. Hope I helped.
EDIT:
I also forgot to mention about William's model, VERY NICE!